animals. Meat taken during the earlier months 

 was preferred to late season kills. The live pack- 

 aging materials recommended for locker use, al- 

 though showing variation in effectiveness, pre- 

 served a good color and prevented freezer burn 

 and weight loss. Flavor, palatability, and tender- 

 ness of ground meat were increased by the addition 

 of fat. Fat also contributed to a moister (juicier) 

 product. Use of the antibiol ic A.ureomycin <>n the 

 meat increased significantly the flavor and accepta- 

 bility scores. 



Population study of bighorn sheep. — The ob- 

 jective- of this investigation were to determine the 

 population dynamics of Rocky .Mountain bighorn 

 sheep on Wildhorse Island (in Flathead Lake) 

 during the years 1959 to 1962, and to bring to- 

 gether information on this population for a 22- 

 year period. The work was conducted by the 

 Montana I nit. 



The number of bighorn sheep on Wildhorse Is- 

 land increased from 2 yearlings in 1939 to 6 sheep 

 (2 rams, 3 ewes, and 1 lamb) in May of 1047, when 

 an additional 7 (3 rams. 3 ewes, and 1 lamb) were 

 released. The herd increased to approximately 

 100 animals by the summer of 1054. Counts for 

 the 4 years 1951) to 1962 were 114. 11-2, 100, and 97. 

 It is considered probable that almost all of the 

 2-year-old ewes produced lambs from initial in- 

 troduction until the peak population was reached. 

 Under the present condition of a stable or declin- 

 ing population, just over 50 percent of the 2-year 

 ewes reproduce. A minimum loss of 114 bighorns 

 can be accounted for since 1952. The heaviest mor- 

 tality of adult bighorns, found dead with horn 

 sheaths intact, was estimated to have occurred dur- 

 ing the sixth year of life in females and during 

 the eighth year in males. The maximum life span 

 of 17 rams (1 year old or older) found dead or 

 dying was estimated to be 10 years. 



Horn growth and aging in bighorn slurp. — A 

 study of 62 bighorn sheep by the Montana Unit 

 showed that horn growth in rains is affected by 

 physiological and environmental conditions, evi- 

 dent from cessat ion and resumpl ion of growth that 

 formed distinct rings, and the retardation of 

 growth that formed secondary or false annuli. 

 Examination of external and internal characteris- 

 tics revealed that horn growth occurred over the 

 entire surface of the bony core and not just at its 

 base. 



Differential growth rates control conformity of 

 the horn. Linear growth was greatest during the 



second year and became increasingly less subse- 

 quently. Definite differences were noted in the 

 formation of distinct annual rings and secondary 

 or false rings. Within limitations of individual 

 variation, the distinct annual rings (true annuli), 

 formed at the end of growth periods, may be used 

 as an indication of age in rams. 



Grizzly bear population study in Yellowstone 

 Park. — In L963, a total of 55 bears were handled 

 (•24 initial captures and 31 recaptures), by Mon- 

 tant Unit personnel, raising the total number for 

 the 5-year study to 282. Thirty-three bears were 

 captured during 28 of 68 t rap-nights, for a success 

 of II percent, an increase of 9 percent over 1962. 

 The remaining 22 animals were shot with drug- 

 filled syringe darts while free-ranging. Twenty- 

 four bears were marked for a 5-year total of 

 165 different grizzlies. Eighty-seven marked 

 bears were theoretically in the population in 1963 

 and 74 were observed 1 or more times. 



The radio-tracking system and a bioeleetronic 

 laboratory were in full operation during 1963. 

 Seven bears were instrumented during 1963 for a 

 total of 13 to date. The last grizzly to receive its 

 transmitter (No. 164) was tracked to its "hiber- 

 nating" den on November 5. The distinctive sig- 

 nal was first received at a distance id' about in 

 miles. Using directional receivers, the source of 

 the signal was located deep in wilderness country 

 during a severe snow storm and the instrumented 

 hear was actually ohserved entering the den. 



I'rrctiry. — For the sixth consecutive year the 

 Arizona Unit and the Arizona Game and Fish 

 Department worked together in manning the L963 

 javelina hunter checking stations. A total of 156 

 animals were handled, and data on weights, gen- 

 eral condition, and age were collected. Aging was 

 determined from the teeth. In addition, attention 

 was given to the possibility of using eyelens for 

 aging, and eyeballs were collected from dead jave- 

 linas for the second consecutive year. 



Further data on javelina reproduction, rate of 

 increase, and food and water requirements were 

 collected from captive animals kept by the Unit. 

 To assist in solving the difficult problem of inter- 

 preting corpora lutea data, females are being 

 sacrificed at known stages of the reproductive 

 cycle. 



Social behavior in swamp rabbits. — A study of 

 social behavior of confined swamp rabbits by the 

 Missouri Unit showed that males have strong so- 

 cial hierarchies. The penned rabbits formed 



34 



